Reward flight taxes

I’ve been looking at booking some UC reward flights for later in the year.
In January there was plenty of availability to NY in Oct with standard G taxes of about £560.
Availability disappeared for a couple of weeks but is now back again.
However - UC taxes are up to £770pp!!!
Is this an error or have taxes gone up on reward flights?

I’ve just done a dummy booking for 10-17 Oct and it’s showing taxes & fees of £562. No idea why you’re seeing £770.

Same as Gumshoe. I'm seeing £570 on an UC redemption to Shanghai.

Just done again and now £560!
Really odd but thanks for checking.